The former Manchester United defender is said to have collapsed before being substituted during a friendly match with Hertha Berlin.
Blind was fitted with a subcutaneous implantable cardioverter defibrillator, a device that monitors and regulates his heart rhythm, after being diagnosed with heart muscle inflammation following a Champions League game with Valencia last December.
Ajax issued a statement via Twitter on Wednesday, saying: "Daley Blind was forced to leave the pitch during Ajax - Hertha BSC.
"The central defender is feeling well, given the circumstances, and was at Sportpark de Toekomst this morning. He will undergo further examinations and await the results of these tests before resuming training."
Netherlands international Blind rejoined Ajax, where he began his career, in 2018 after spending four years with United.
Ajax are due to begin their Eredivisie season on September 13. The 2019-20 campaign was suspended in March due to the coronavirus pandemic before being declared void a month later.
The 34-year-old is appearing at his fourth major tournament with the Oranje, who he represented at the 2014 and 2022 World Cups, as well as Euro 2020.
However, his playing involvement has been far more limited this time around, with the defender only appearing for the final minute of the 3-0 victory over Romania in the round of 16.
Blind was made aware this would be the case ahead of the tournament following a discussion with head coach Ronald Koeman, who encouraged him to use his vast experience to benefit the younger players in the squad.
"It's different, and it takes some getting used to," the Girona defender told reporters at a press conference on Thursday. "In this role, you try to help your team-mates, keeping them sharp and motivated. Some have it hard at times.
"You want to play yourself, of course, but it is a choice the coach has made, and I try to be a helping hand where necessary. I knew what my role would be after speaking to the coach before the tournament started.
"But the fact that this was going to be my role never meant for a moment that I didn't want to come to the tournament. It's a great honour to play for the Dutch team, and certainly at a final tournament."
The Netherlands are gearing up for a quarter-final showdown with Turkiye in Berlin on Saturday.
England or Switzerland will await the winners in the last four, where the Oranje are aiming to advance for the first time in this competition since 2004.
"Hopefully, it will be a great match," Blind added. "Turkiye bring a lot of emotion and passion, so we'll have to be wary of that. It is a quarter-final at a major tournament, and that is always a tough event."
The Netherlands defender had been heavily linked with Royal Antwerp, but he jumped at the chance to join Bundesliga leaders Bayern.
Blind has committed to a six-month contract, with the 32-year-old adding the Bavarian giants to his illustrious list of clubs, having also had a four-year stint at Manchester United that ended in 2018.
"We're delighted that Daley is joining our team. Daley is a versatile defender, capable of playing on the left or in the centre. He has great international experience and leadership qualities. I'm sure he'll help us," sporting director Hasan Salihamidzic said.
Blind travelled to Germany on Thursday before undergoing a medical with Bayern. He has an implantable cardioverter-defibrillator, a device similar to a pacemaker, after being diagnosed in December 2019 with a heart condition.
That proved no obstacle to him signing, with Blind now set to feature as Julian Nagelsmann's side chase domestic and European honours.
Speaking on his transfer, Blind confirmed fighting for such trophies was a key factor in his decision: "I can hardly wait to play here. We’ve got the most important part of the season coming up, where it’s about titles – and a club like Bayern can win every trophy.
"The hunger for titles here at the club was key in my decision. I hope I can bring my experience to help the team. I’ll give everything for Bayern Munich."
With a four-point cushion over Freiburg, they lead the way in the Bundesliga after 15 games, while in the Champions League they face a testing last-16 clash against Paris Saint-Germain.
Blind scored for the Netherlands during their World Cup campaign in Qatar, netting in the 3-1 win over the United States at the last-16 stage.
He has 99 caps for his country and will be looking to complete a century in the early stages of Ronald Koeman's second spell in charge.
Across two spells at Ajax, he made over 300 appearances and won the Eredivisie on seven occasions – only Johan Cruyff and Sjaak Swart won more league titles with the Amsterdam giants with eight apiece.
He was formally released by the Dutch champions on December 27, with Ajax chief executive Edwin van der Sar saying at the time: "I hope he can find another club to end his successful career with."
Ajax said on Tuesday that Netherlands international Blind underwent a series of examinations following the incident that forced his substitution in the 1-0 win at the Johan Cruijff ArenA on August 25 and has been deemed fit to return.
The former Manchester United player was fitted with a subcutaneous implantable cardioverter defibrillator – a device that monitors and regulates his heart rhythm – after being diagnosed with heart muscle inflammation following a Champions League game with Valencia last December.
An Ajax statement read: "Daley Blind is training again with the Ajax first team. In a friendly match against Hertha Berlin on Tuesday, August 25th, the defender had to be substituted.
"Afterwards, Blind underwent a series of examinations which meant he was also unavailable for the Dutch national team.
"The results of the examinations concluded that there was no reason for Blind to stay on the sidelines any longer.
"Last week, the second captain began training in phases and this week he returned to full training."
Ajax are scheduled to begin their 2020-21 Eredivisie campaign away to Sparta Rotterdam on Sunday.
Lodeweges, who was assistant to Ronald Koeman until his departure to Barcelona earlier this month, had the responsibility of selecting the full squad for the first time.
He has taken the opportunity to introduce fresh faces and recall some familiar ones not seen in the selection for several years, while Juventus centre-back Matthijs de Ligt remains sidelined after knee surgery.
Attacking midfielder Ihattaren impressed in his 22 Eredivisie appearances for PSV in 2019-20 and declared for the Netherlands last year having also been eligible for Morocco.
Ball-playing centre-back Schuurs broke into Ajax's first-team squad before Dutch football was halted by the coronavirus pandemic.
Similarly, attack-minded left-back Wijndal – also 20 years old, like Ihattaren and Schuurs – earned rave reviews with AZ prior to the 2019-20 campaign being cancelled.
While those three will be hoping for their first caps, Leroy Fer and Tim Krul are aiming to return to action with the national side after significant periods away.
Krul last played for his country in October 2015, while Fer's absence has been 11 months longer – he featured most recently against Mexico in November 2014.
Daley Blind was among several on the provisional list, but he has been discarded after a recent health scare in an Ajax friendly.
The centre-back, who was last year fitted with a subcutaneous implantable cardioverter defibrillator after being diagnosed with heart muscle inflammation, collapsed in the meeting with Hertha Berlin but insisted he was "feeling fine" when he provided an update on Wednesday.
Myron Boadu, Teun Koopmeiners and Calvin Stengs were among the more surprising omissions of those on the provisional list.
The Netherlands face Poland on September 4 and Italy three days later.
Netherlands squad in full:
Jasper Cillessen (Valencia), Marco Bizot (AZ), Tim Krul (Norwich City); Virgil van Dijk (Liverpool), Denzel Dumfries (PSV), Nathan Ake (Manchester City), Hans Hateboer (Atalanta), Perr Schuurs (Ajax), Joel Veltman (Brighton and Hove Albion), Stefan de Vrij (Inter), Owen Wijndal (AZ); Donny van de Beek (Ajax), Leroy Fer (Feyenoord), Mohamed Ihattaren (PSV), Frenkie de Jong (Barcelona), Marten de Roon (Atalanta), Kevin Strootman (Marseille), Georginio Wijnaldum (Liverpool); Luuk de Jong (Sevilla), Quincy Promes (Ajax), Ryan Babel (Galatasaray), Steven Bergwijn (Tottenham).
